Description:
------------
We have serialized object of class A and array with 2 such objects

<?php
class A {}

echo serialize(new A()).PHP_EOL;
echo serialize(array(new A(), new A())).PHP_EOL;
?>

Then we write autoload function which throws exception if can't find a file with 
class.

And in first case - we have a normal behaviour (we can catch exception).
In second we have uncaughted exception. 

Test script:
---------------
<?php
  spl_autoload_register(
    function($class) {
  		if (!file_exists($class.'.php'))
  			throw new Exception();

  		require_once $class.'.php';
  	}
  );
  
  try {
    var_dump(unserialize('O:1:"A":0:{}'));
    echo 'Serialized'.PHP_EOL;
  } catch (Exception $e) { 
    echo 'Failed'.PHP_EOL;
  }
  
  try {
    var_dump(unserialize('a:2:{i:0;O:1:"A":0:{}i:1;O:1:"A":0:{}}'));
    echo 'Serialized'.PHP_EOL;
  } catch (Exception $e) { 
    echo 'Failed'.PHP_EOL;
  }

Expected result:
----------------
Failed
Failed

Actual result:
--------------
Failed
PHP Fatal error:  Uncaught exception 'Exception' in -:5
Stack trace:
#0 [internal function]: {closure}('A')
#1 [internal function]: spl_autoload_call('A')
#2 -(20): unserialize('a:2:{i:0;O:1:"A...')
#3 {main}

Next exception 'Exception' in -:5
Stack trace:
#0 [internal function]: {closure}('A')
#1 -(0): spl_autoload_call('A')
#2 {main}
  thrown in - on line 5